Patients unable to ingest food can be provided with nourishment through the use of feeding tubes. Feeding tubes preferably are positioned to deliver enteral nutritional products to the patient's stomach or small bowel.
Feeding tubes are positioned in a patient using two primary methods. First, a feeding tube can be inserted through the patient's nose such that it passes through the esophagus and into the stomach or small bowel. Alternatively, feeding tubes can be placed percutaneously such that they pass through the patient's abdominal wall and directly into the patient's stomach. The feeding tube can be placed in the patient's small bowel using the percutaneous placement method by passing the feeding tube through the patient's abdominal wall, through the patient's stomach, and into the patient's small bowel. Feeding tubes also can be placed percutaneously directly into the patient's small bowel.
Regardless of the method by which the feeding tube is placed in a patient, it is necessary to confirm that the distal end of the feeding tube is positioned properly within the patient's gastrointestinal tract. Improper placement of the distal end of the feeding tube can result in negative health consequences. For example, it is possible that a nasogastric tube will inadvertently be placed in the patient's respiratory system, i.e., in the patient's tracheobronchial tree, in the patient's pleural space, or in the patient's lung. If an enteral nutritional product is delivered to a patient having such an inadvertently placed feeding tube, the enteral nutritional product will be delivered to the patient's respiratory system, thereby creating the potential for damage to the patient's respiratory system. For this reason, it is important to confirm that a feeding tube is not placed in the patient's respiratory system prior to the delivery of an enteral nutritional product through the feeding tube.
It also is possible for feeding tubes to "double back" during placement. For example, if a nasointestinal feeding tube is being placed into the small bowel, the feeding tube is fed through the patient's esophagus and stomach until it is properly positioned within the small bowel. However, due to the anatomy of the stomach and the pylorus, it is possible for the feeding tube to reverse directions in the stomach and return to the esophagus as it is fed into the patient. Thus, the distal end of the feeding tube may inadvertently be placed in the patient's esophagus rather than in the patient's small bowel. The positioning of the feeding tube in the esophagus also may have detrimental health consequences as there is an increased risk that an enteral nutritional product delivered through such a feeding tube will migrate to the patient's respiratory system, e.g., as a result of aspiration by the patient.
In some cases it is important to confirm the precise location of the feeding tube within the patient's gastrointestinal tract. For example, it may be preferable to place the feeding tube in the patient's small bowel in order to reduce the likelihood that the enteral nutritional product will be aspirated by the patient. The potential for aspiration exists when fluids move upwardly into the patient's esophagus, thereby creating an opportunity for the fluids to migrate into the patient's respiratory system. The potential for aspiration is decreased when an enteral nutritional product is delivered into the patient's small bowel. The patient's disease state may also dictate a preferred placement of the distal end of the feeding tube.
The most common methodologies for determining feeding tube placement are (a) radiography; and (b) auscultation. Radiographic techniques require that the patient be subjected to X-rays for the purpose of determining the precise location of the distal end of the feeding tube. Such techniques can be time consuming due to the fact that the patient must be moved to an X-ray laboratory in order to confirm feeding tube placement. Alternatively, a portable X-ray apparatus may need to be transported to the patient's bedside to confirm feeding tube placement. In addition, X-ray verification of feeding tube placement is a relatively costly procedure. Finally, safety concerns regarding the exposure of patient's to X-rays must be considered.
Auscultation entails the introduction of air through the feeding tube. As the air is introduced into the patient's feeding tube, a medical professional uses a stethoscope to listen for abdominal sounds produced by the air. A failure to clearly hear loud sounds may indicate that the feeding tube has been inadvertently placed in the patient's respiratory system instead of the gastrointestinal tract. However, auscultation may be inconclusive because sounds may be transmitted to the abdominal area even when the feeding tube is in the respiratory system. For example, it has been found that a minor gurgling sound may be referred to the gastrointestinal tract in some patients even though the distal end of the feeding tube is positioned within the patient's respiratory tract or in the patient's pleural space. This minor gurgling sound can be misinterpreted as an indication that the feeding tube is placed correctly in the gastrointestinal tract.
An alternative methodology for determining feeding tube location entails the placement of the proximal end of the feeding tube (the end positioned external to the patient) in a container of liquid. This methodology theorizes that a feeding tube inadvertently placed in a patient's respiratory system will produce bubbles in the liquid as the patient exhales. However, placement of the feeding tube in bronchioles may occlude the port or ports on the distal end of the feeding tube, thereby precluding the passage of air through the tube. Alternatively, the port or ports of the feeding tube may be lodged against pleural tissues, thereby precluding the passage of air through the tube.
Yet another methodology for determining feeding tube location entails the monitoring of the patient for signs of respiratory distress such as coughing, dyspnea, or cyanosis. This methodology may be inconclusive in patients having decreased levels of consciousness, diminished cough or gag reflexes, and/or temporary laryngeal incompetence. Further, the delivery of even a small amount of an enteral nutritional product into a patient's respiratory system may produce deleterious health consequences. Thus, merely waiting for the manifestations of improper feeding tube placement may not be adequate for many patients.
U.S. Pat. No. 3,373,735 to Gallagher discloses a method for determining feeding tube location using the pH of fluids aspirated through the feeding tube. However, this methodology also has drawbacks in that fluids aspirated from both the small bowel and the respiratory system are usually alkaline while gastric fluids are acidic. Thus, the pH method can be used to confirm gastric placement, but cannot be used to differentiate between placement in the respiratory system and placement in the small bowel. Further, medications can significantly increase the pH of gastric fluids, thereby rendering the pH methodology useless in certain groups of patients.